The term heating item, in the context of the present invention, refers to an item equipped with its own heating system or an item that is heated by an exterior system and that is capable of transmitting the heat energy introduced by this system to a third material or object in contact with said item, or an item intended to receive another item that has previously been heated.
The term sol-gel coating, in the context of the present invention, refers to a coating synthesized through a sol-gel process from a solution of liquid phase precursors into a solid through a set of chemical reactions (hydrolysis and condensation) at low temperatures. The resulting coating may be either organo-mineral or entirely mineral.
The term organo-mineral coating, in the context of the present invention, refers to a coating for which the network is essentially inorganic, but which includes organic groups, due particularly to the precursors used and the temperature at which the coating is cooked, or due to the incorporation of organic loads.
The term entirely mineral coating, in the context of the present invention, refers to a coating comprised of an entirely inorganic material, free of any organic groups. Such a coating may also be obtained through a sol-gel process with a cooking temperature of at least 400° C., or through the use of tetraethyl orthosilicate (TEOS) type precursors with a cooking temperature that may be less than 400° C.
For a number of years, sol-gel coatings have been gaining preference over coatings based on fluorocarbon resins such as polytetrafluoroethylene (PTFE), for the purposes of creating non-stick coatings for culinary items. However, sol-gel coatings must still be applied to formed, previously stamped items, as inorganic networks cannot be formed without cracking. This translates to a significant reduction in the adherence of the sol-gel coating to the substrate, in addition to a lower resistance to grease penetration in the case of a culinary item in use. In terms of manufacturing, sol-gel coatings are applied to items that have already been stamped. Thus, they cannot be applied with many plate-coating techniques (screen printing, roller, ink jet, curtain coating, etc.), and are generally applied by powder coating with a pneumatic gun. This results in a significant loss of the product during the powder coating (depending on the item's shape, the loss may constitute 30 to 70% of the applied sol-gel composition), and potentially the overspray of the product onto the surface opposite the coated surface, which may be difficult to control.
This is not the case for fluorocarbon coatings (having the ability to be formed, and in particular, drawn), which may be formed and stamped, and are therefore applied onto flat surfaces using plate coating methods prior to thermal treatments and stamping into the desired shape.